1. FIELD OF THE INVENTION
The present invention relates to a method of producing an improved composite-composite structure for aircraft or aerospace use. The method and articles produced thereby generally involve pyrolyzing a loosely woven organic or inorganic fiber/binder in the shape of a honeycomb, depositing a ceramic material onto the carbonized fabric, optionally removing the pyrolyzed organic fabric and depositing the same or a different ceramic material onto and within the hollow honeycomb structure.
2. DESCRIPTION OF THE PRIOR ART
In the present art, polymeric, metallic and ceramic structures have been produced at low temperatures or in situations wherein weight requirements are not of concern. Structures having intricate designs, such as honeycomb structures, have not been described.
In U.S. Pat. No. 4,488,920, L. J. Danis discloses a process of making a large scale ceramic heat exchanger by separately forming grooved components and bonding these components together by chemical vapor deposition.
In U.S. Pat. No. 4,515,860, R. A. Holzl discloses a method for coating carbon bodies to protect them at elevated temperatures.
In U.S. Pat. No. 4,476,178, R. D. Veltri et al., disclose a multilayered coating system for the protection of carbon-carbon composites. Silicon carbide is diffused onto a carbon substrate which successfully protects the carbon-carbon material from oxidation at temperatures up to 2,500.degree. F. and higher. These references individually or collectively do not disclose the present invention.
One approach to produce ceramic honeycomb structures is to extrude ceramic forms having the following shapes: ##STR1## The two shapes are layered one on top of the other so that the flat portions are mated and a regular honeycomb structure is obtained. These points of juncture are then either adhered to each other using ceramic adhesive or are fused together using deposition or simply using elevated temperature. The honeycomb has hexagonal solid sides and hexaon-shaped openings therebetween. This method is long, involved, requires extensive hand labor and is expensive.
Previous attempts to produce ceramic-ceramic honeycomb structures by deposition have used porous substrates with uneven pore size distributions. These configurations have caused slow deposition rates and also pore blockage reducing penetration of the ceramic into the substrate. It is therefore desirable to develop a method to produce ceramic honeycomb based materials which have increased structure stability, improved physical properties, lighter weight properties, better high temperature limits (e.g., between about 700.degree. to 1,800.degree. C.) and the like.
It is an object of the present invention to provide a process and articles thereof wherein an organic, inorganic or metallic fabric made rigid in an organic binder or an organic fabric and an inorganic binder is used as a honeycomb form for the chemical vapor deposition/chemical vapor infiltration/deposition of a ceramic material to produce the corresponding ceramic honeycomb.
It is an object of the present invention to provide a process to obtain a ceramic coated pyrolyzed organic polymer/fabric honeycomb structure.
It is another object of the present invention to provide a process to obtain a ceramic honeycomb wherein the carbon-based fabric/binder honeycomb internal structure has been removed.
It is still another object of the present invention to provide a process to obtain a ceramic object which is formed by first depositing ceramic in all of the holes of the honeycomb fabric and or binder structure left by pyrolyzing and removing the organic components.
It is still another object to provide a process to obtain a ceramic object formed when the ceramic is deposited upon the degradable honeycomb structure, the honeycomb structure is removed and the voids created by removal are filled with more ceramic material.